Asymmetrical surgical stapling device

ABSTRACT

An endoscopic stapling device for tissue resection has an asymmetrical tool assembly that delivers a greater number of staples, or rows of staples, to healthy tissue that remains in a patient, and fewer number of staples, or rows of staples, to diseased or damaged tissue to be resected and removed from the patient. The tool assembly includes an asymmetric cartridge assembly and an asymmetric anvil assembly for applying the staples to the resected and healthy tissues. The endoscopic stapling device also includes an asymmetric drive assembly for actuating the tool assembly.

FIELD

This technology is generally related to surgical stapling devices and, more particularly, to surgical stapling devices with asymmetrical tool assemblies.

BACKGROUND

Surgical stapling devices for endoscopic or laparoscopic use are well known and commonly used to minimize patient trauma and reduce patient recovery times. Typically, endoscopic stapling devices include a tool assembly that has an anvil assembly and a cartridge assembly that are coupled to each other by a pivot member and movable in relation to each other between open and clamped positions. The cartridge assembly includes a channel member that supports a staple cartridge that is fixedly or removably supported within the channel member. The staple cartridge defines a central knife slot and staple receiving pockets that are positioned on each side of the central knife slot. Each of the staple receiving pockets of the staple cartridge receives a staple.

Typically, the staple cartridge is symmetrical, i.e., the staple receiving pockets in the staple cartridge are aligned in an equal number of rows on each side of the central knife slot. When tissue is resected during a surgical procedure to, e.g., remove diseased or damaged tissue from a patient, a drive assembly is advanced through the central knife slot of the staple cartridge to eject the staples from the staple cartridge and cut tissue clamped between the anvil and cartridge assemblies. After the stapling procedure, the resected tissue is removed and disposed of as desired with the rows of staples from one side of the central knife slot received in the resected tissue. The rows of staples from the other side of the central knife slot are applied to healthy tissue of the patient and remains within the patient.

The size of the tool assembly of an endoscopic stapling device is limited by the size of a cannula through which the stapling device is inserted to access a body cavity. Thus, the size of the staple cartridge and the number of rows of staples formed in the staple cartridge are limited.

A continuing need exists in the art for an endoscopic stapling device having a tool assembly that makes better use of the available space.

SUMMARY

This disclosure is directed to an endoscopic stapling device for tissue resection that has an asymmetrical tool assembly for delivering a greater number of staples, or rows of staples, to healthy tissue that remains in a patient, and fewer number of staples, or rows of staples, to diseased or damaged tissue to be resected and removed from the patient. The tool assembly includes an asymmetric cartridge assembly and an asymmetric anvil assembly for applying the staples to the resected and healthy tissues. The endoscopic stapling device also includes an asymmetric drive assembly for actuating the tool assembly.

Aspects of this disclosure are directed to a tool assembly including an anvil assembly and a cartridge assembly. The anvil assembly includes an anvil plate having a staple forming surface. The anvil plate defines a knife slot and staple forming pockets that are positioned on opposite sides of the knife slot in the anvil plate. The cartridge assembly is coupled to the anvil assembly such that the tool assembly is movable between open and clamped positions. The cartridge assembly includes a channel member and a staple cartridge. The channel member has side walls and a bottom wall that define a cavity. The bottom wall of the channel member defines a knife slot. The staple cartridge is received within the cavity of the channel member and includes a cartridge body, staples, pushers, and an actuation sled. The cartridge body defines a knife slot and staple receiving slots that are positioned on opposite sides of the knife slot of the cartridge body. The knife slot in the channel member is axially aligned with the knife slot in the cartridge body. Each of the staple receiving slots receives one of the staples and one of the pushers, and the actuation sled is movable within the cartridge body into engagement with the pushers to sequentially eject the staples from the cartridge body. The tool assembly defines a central longitudinal axis, and the knife slots of the anvil plate, the channel member, and the cartridge body of the staple cartridge are laterally offset from the central longitudinal axis of the tool assembly.

Other aspects of the disclosure are directed to a cartridge assembly that includes a channel member and a staple cartridge. The channel member includes side walls and a bottom wall that define a cavity. The bottom wall of the channel member defines a knife slot. The staple cartridge is received within the cavity of the channel member and includes a cartridge body, staples, pushers, and an actuation sled. The cartridge body defines a knife slot and staple receiving slots. The staple receiving slots are positioned on opposite sides of the knife slot of the cartridge body. The knife slot in the channel member is axially aligned with the knife slot in the cartridge body. Each of the staple receiving slots receives one of the staples and one of the pushers. The actuation sled is movable within the cartridge body into engagement with the pushers to sequentially eject the staples from the cartridge body. The cartridge assembly defines a central longitudinal axis, and the knife slots of the channel member and the cartridge body are laterally offset from the central longitudinal axis of the tool assembly.

Another aspect of the disclosure is directed to a staple cartridge that includes a cartridge body, staples, pushers, and an actuation sled. The cartridge body defines a knife slot and staple receiving slots. The staple receiving slots are positioned on opposite sides of the knife slot. The staples are received within the staple receiving slots of the cartridge body. The pushers are received within the staple receiving slots of the cartridge body. Each of the pushers supports one of the staples. The actuation sled is positioned within the cartridge body and is movable within the cartridge body into engagement with the pushers to sequentially eject the staples from the cartridge body. The staple cartridge defines a central longitudinal axis, and the knife slot in cartridge body is laterally offset from the central longitudinal axis of the staple cartridge.

In aspects of the disclosure, the knife slot in the anvil plate divides the staple forming surface of the anvil plate into a first surface that is positioned on a first side of the knife slot in the anvil plate and a second surface that is positioned on a second side of the knife slot in the anvil plate.

In some aspects of the disclosure, the staple forming pockets are aligned in rows in the first and second surfaces of the staple forming surface.

In certain aspects of the disclosure, the first surface of the staple forming surface has a greater number of rows of the staple forming pockets than the second surface of the staple forming surface.

In aspects of the disclosure, the knife slot of the cartridge body divides the tissue engaging surface of the cartridge body into a first surface that is positioned on a first side of the knife slot in the cartridge body and a second surface that is positioned on a second side of the knife slot in the cartridge body.

In some aspects of the disclosure, the staple receiving slots are aligned in rows in the first and second surfaces of the tissue engaging surface.

In certain aspects of the disclosure, the first surface of the tissue engaging surface has a greater number of rows of the staple receiving slots than the second surface of the tissue engaging surface.

In aspects of the disclosure, the first surface of the staple forming surface has four rows of the staple forming pockets and the second surface of the staple forming surface has two rows of the staple forming pockets, and the first surface of the tissue engaging surface has four rows of the staple receiving slots and the second surface of the tissue engaging surface has two rows of the staple receiving slots.

In some aspects of the disclosure, the actuation sled includes a body having a guide member and cam members.

In certain aspects of the disclosure, two of the cam members are positioned on a first side of the guide member and one of the cam members is positioned on a second side of the guide member.

In aspects of the disclosure, the tool assembly has a drive assembly that includes a drive member and an I-beam that is movable through the anvil and cartridge assemblies to advance the actuation sled from its retracted position to its advanced position.

In some aspects of the disclosure, the I-beam includes a first beam, a second beam, and a vertical strut that extends through the knife slots of the anvil plate, the cartridge body, and the channel member.

In certain aspects of the disclosure, the vertical strut includes a cutting blade, and the tissue engaging surface of the cartridge body and the staple forming surface of the anvil plate define a tissue gap.

In aspects of the disclosure, the cutting blade is positioned within the tissue gap when the tool assembly is in a clamped position.

In some aspects of the disclosure, each of the first and second beams of the I-beam includes first and second overhangs that extend in cantilevered fashion from opposite sides of the vertical strut.

In certain aspects of the disclosure, the first overhang has a length that is greater than a length of the second overhang.

Other features of the disclosure will be appreciated from the following description.

BRIEF DESCRIPTION OF DRAWINGS

Various aspects of the disclosure are described herein below with reference to the drawings, wherein:

FIG. 1 is a side perspective view of a surgical stapling device according to aspects of the disclosure with a tool assembly in an open position;

FIG. 2 is an enlarged view of the indicated area of detail shown in FIG. 1 ;

FIG. 3 is an enlarged view of the tool assembly of the stapling device shown in FIG. 1 in the open position showing a tissue engaging surface of the anvil assembly;

FIG. 4 is an exploded, side perspective view of the tool assembly of the stapling device shown in FIG. 1 ;

FIG. 5 is an enlarged view of the indicated area of detail shown in FIG. 4 ;

FIG. 6 is an enlarged view of the indicated area of detail shown in FIG. 4 ;

FIG. 7 is a side perspective view of the tool assembly shown in FIG. 2 in a clamped position about tissue;

FIG. 8 is a cross-sectional view taken along section line 8-8 of FIG. 7 ; and

FIG. 9 is a side perspective view of a resected tissue section and a healthy tissue section after the tissue has been resected with the stapling device shown in FIG. 1 .

DETAILED DESCRIPTION

The disclosed surgical stapling device will now be described in detail with reference to the drawings in which like reference numerals designate identical or corresponding elements in each of the several views. However, it is to be understood that the aspects of the disclosure are merely exemplary and may be embodied in various forms. Well-known functions or constructions are not described in detail to avoid obscuring the disclosure in unnecessary detail. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the disclosure in virtually any appropriately detailed structure.

In this description, the term “proximal” is used generally to refer to that portion of the device that is closer to a clinician during use of the device in its customary manner, while the term “distal” is used generally to refer to that portion of the device that is farther from the clinician during use of the device in its customary manner. In addition, the term “clinician” is used generally to refer to medical personnel including doctors, nurses, and support personnel. Further, directional terms such as front, rear, upper, lower, top, bottom, and similar terms are used to assist in understanding the description and are not intended to limit the disclosure.

This disclosure is directed to an endoscopic stapling device for tissue resection that has an asymmetrical tool assembly for delivering a greater number of staples, or rows of staples, to healthy tissue that remains in a patient, and fewer number of staples, or rows of staples, to diseased or damaged tissue to be resected and removed from the patient. The tool assembly includes an asymmetric cartridge assembly and an asymmetric anvil assembly for applying the staples to the resected and healthy tissues. The endoscopic stapling device also includes an asymmetric drive assembly for actuating the tool assembly.

FIG. 1 illustrates exemplary aspects of the disclosed surgical stapling device shown generally as stapling device 10. The stapling device 10 includes a handle assembly 12, an elongate body 14 that defines a longitudinal axis “X”, and a tool assembly 16. The handle assembly 12 includes a stationary handle 18 and a trigger 20 that is movable in relation to the stationary handle 18 to actuate the tool assembly 16. In aspects of the disclosure, the stapling device 10 includes a rotation knob 22 and an articulation lever 24. The rotation knob 22 is coupled to the handle assembly 12 and supports the elongate body 14 to facilitate rotation of the elongate body 14 and tool assembly 16 in relation to the handle assembly 12 about the longitudinal axis “X”. The articulation lever 24 is coupled to the tool assembly 16 and operates an articulation mechanism (not shown) supported within the elongate body 14 to articulate the tool assembly 16 about an articulation axis “Z” from a position aligned with the longitudinal axis “X” to positions that define acute angles with the longitudinal axis “X”. In some aspects of the stapling device 10, the handle assembly 12 includes retraction knobs 26 that can be pulled proximally to retract a drive assembly of the stapling device 10. For a more detailed description of exemplary aspects of the handle assembly 12 of the stapling device 10, see, e.g., U.S. Pat. No. 6,241,139 (“the '139 Patent”). Although the handle assembly 12 is illustrated as a manually operated handle assembly, it is envisioned that the handle assembly 12 could be a powered handle assembly such as described in U.S. Pat. No. 9,055,943.

In aspects of the disclosure, the tool assembly 16 forms part of a reload assembly 27 which includes a body portion 27 a and the tool assembly 16. The body portion 27 a has a proximal end that is releasably coupled to the elongate body 14 and a distal end that supports the tool assembly 16. In aspects of the disclosure, the tool assembly 16 is coupled to the body portion 27 a by a pivot member 29 that defines the articulation axis “Z” such that the tool assembly 16 can pivot about the articulation axis “Z” in response to operation of the articulation lever 24. It is envisioned that the tool assembly 16 can be directly coupled to the elongate body 14 and need not form part of a reload assembly 27.

FIGS. 2-4 illustrate the tool assembly 16 of the stapling device 10 (FIG. 1 ). The tool assembly 16 defines a central longitudinal axis “X1” (FIG. 7 ) and includes an anvil assembly 28 and a cartridge assembly 30 that are movable in relation to each other between an open position (FIG. 1 ) and a clamped position (FIG. 7 ). In aspects of the disclosure, the anvil 28 and the cartridge assembly 30 are coupled together with pivot members 32 such that the cartridge assembly 30 can pivot in relation to the anvil 30 between the open and clamped positions. Although the cartridge assembly 30 is illustrated as being pivotable towards the stationary anvil 28, it is envisioned that the anvil 30 could be adapted to pivot towards a stationary cartridge assembly 30.

The anvil assembly 28 includes a body portion 34 and an anvil plate 36. The anvil plate 36 has an outer surface that defines a channel 38 (FIG. 8 ) and an inner staple forming surface 40 (FIG. 3 ). The anvil plate 36 also defines a knife slot 42 that is laterally offset from the central longitudinal axis “X1” of the tool assembly 16 and extends longitudinally through the anvil plate 36. The knife slot 42 divides the staple forming surface 40 into a first surface 40 a that is positioned on a first side of the knife slot 42 and a second surface 40 b that is positioned on a second side of the knife slot 42.

The first and second surfaces 40 a, 40 b of the staple forming surface 40 of the anvil plate 36 each define one or more rows of staple forming pockets 44 (FIG. 3 ). In aspects of the disclosure, the first surface 40 a of the staple forming surface 40 includes a greater number of rows of staple forming pockets 44 than the second surface 40 b of the staple forming surface 40. In some aspects of the disclosure, the first surface 40 a of the staple forming surface 40 of the anvil plate 36 defines four rows of staple forming pockets 44 and the second surface 40 b of the staple forming surface 40 defines two rows of staple forming pockets 44. Alternately, it is envisioned that the first surface 40 a of the staple forming surface 40 can define two or more rows of staple forming pockets 44 and the second surface 40 b can define one or more rows of staple forming pockets 40, so long as the number of staple forming pockets 40 defined in the first surface 40 a of the anvil plate 36 is greater than the number of staple forming pockets 40 defined in the second surface 40 b of the anvil plate 36. In some aspects of the disclosure, the anvil assembly 28 includes indicia, e.g., arrows 41 (FIG. 1 ) that identify to a clinician the position of the first side 40 a of the staple forming surface 40 b in relation to the second side 40 b of the staple forming surface 40.

The body portion 34 of the anvil assembly 28 includes a base 50 and an extension 52 that projects distally from the base 50. The extension 52 is secured to the anvil plate 36 and encloses the channel 38 in the anvil plate 36. The base 50 has a semi-circular configuration and includes tissue stops 54 that are aligned with the proximal-most staple forming pockets 44. The tissue stops 54 are positioned to obstruct passage of tissue proximally beyond the staple forming pockets 44. The base 50 defines openings 56 that receive the pivot members 32 (FIG. 4 ) to couple the anvil assembly 28 to the cartridge assembly 30. The body portion 34 of the anvil assembly 28 includes a bracket 58 that facilitates coupling the tool assembly 16 to the elongate body 14 (FIG. 1 ) for articulation about the articulation axis “Z”. For a detailed description of a coupling for securing the tool assembly 16 to the elongate body 14, see, e.g., the '139 Patent.

The cartridge assembly 30 includes a staple cartridge 62 and a channel member 64. The channel member 64 includes side walls 66 and a bottom wall 68 that together define a cavity 70 that receives the staple cartridge 62. The bottom wall 68 includes an outer surface that defines a recess 68 a (FIG. 8 ) that extends longitudinally along the channel member 64. In aspects of the disclosure, the staple cartridge 62 is releasably supported within the cavity 70 of the channel member 64 and can be replaced to facilitate reuse of the stapling device 10 (FIG. 1 ). The channel member 64 defines a knife slot 69 that is laterally offset from the longitudinal axis “X1” (FIG. 7 ) of the tool assembly 16. The channel member 64 also defines openings 71 (FIG. 2 ) that receive the pivot members 32 to pivotably couple the cartridge assembly 30 to the anvil assembly 28.

The staple cartridge 62 includes a cartridge body 72, staples 74, pushers 76, and an actuation sled 78. The cartridge body 72 includes a tissue engaging surface 73 and defines a knife slot 80 and staple receiving slots 82. The staple receiving slots 82 are positioned on opposite sides of the knife slot 80. Each of the staple receiving slots 82 in the cartridge body 72 receives one of the staples 74 and a pusher 76. The knife slot 80 is laterally offset from the longitudinal axis “X1” (FIG. 7 ) of the tool assembly 16 and is aligned with the knife slot 69 in the channel member 64. The knife slot 80 divides the tissue engaging surface 73 of the cartridge body 72 into a first surface 73 a that is positioned on a first side of the knife slot 80 and a second surface 73 b that is positioned on a second side of the knife slot 80.

The first and second surfaces 73 a, 73 b of the cartridge body 72 each define one or more rows of staple receiving slots 82 (FIG. 2 ). In aspects of the disclosure, the first surface 73 a of the cartridge body 72 includes a greater number of rows of staple receiving slots 82 than the second surface 73 b of the cartridge body 72. In some aspects of the disclosure, the first surface 73 a of the cartridge body 72 of the staple cartridge 62 defines four rows of staple receiving slots 80 and the second surface 73 b of the cartridge body 72 of the staple cartridge 62 defines two rows of staple receiving slots 82. Alternately, it is envisioned that the first surface 73 a of the cartridge body 72 can define two or more rows of staple receiving slots 82 and the second surface 73 b of the cartridge body 72 can define one or more rows of staple receiving slots 82, as long as the number of staple receiving slots 82 defined in the first surface 73 a of the staple receiving slots 82 is greater than the number of staple receiving slots 82 defined in the second surface 73 b of the cartridge body 72.

The actuation sled 78 (FIG. 5 ) is positioned within a proximal portion of the cartridge body 72 and is movable from a retracted position to an advanced position to eject the staples 74 from the staple receiving slots 82. The actuation sled 78 includes a body 84 that has a guide member 86 and cam members 88 that are positioned on opposite sides of the guide member 86. The guide member 86 is received in the knife slot 80 of the staple cartridge 62. The cam members 88 are positioned to sequentially engage the pushers 76 when the actuation sled 78 is moved from the retracted position towards the advanced position to lift the pushers 76 within the staple receiving slots 82 and eject the staples 74 from the staple receiving slots 82.

In aspects of the disclosure, the actuation sled 78 includes two cam members 88 on a first side of the guide member 86 and one cam member 88 on a second side of the guide member 86. The first side of the guide member 86 is aligned with the first surface 73 a of the cartridge body 72 and the second side of the guide member 86 is aligned with the second surface 73 b of the cartridge body 72.

FIGS. 4 and 6 illustrate a drive assembly 90 of the stapling device 10 (FIG. 1 ) which includes a drive member 92 and an I-beam 94 that is supported on a distal end of the drive member 92. In aspects of the disclosure, the drive member 92 includes a proximal portion that supports a coupling member 96 that is configured to be releasably coupled to a drive rod (not shown) in the elongate body 14 (FIG. 1 ) such that axial movement of the drive rod (not shown) causes axial movement of the drive assembly 90. The drive member 92 is formed of a resilient material, e.g., spring steel, that allows the drive member 92 to bend about the articulation axis “Z”. In aspects of the disclosure, the drive member 92 is formed from stacked sheets of material although the use of other resilient drive members is envisioned.

The I-beam 94 includes first and second beams 100, 102 and a vertical strut 104 that connects the first beam 100 to the second beam 102. The vertical strut 104 is secured to the first and second beams 100, 102 at a position laterally offset from the longitudinal axis “X1” (FIG. 7 ) of the tool assembly 16 and laterally offset from a central axis of the first and second beams 100, 102. In aspects of the disclosure, the first beam 100 of the I-beam 94 has a first overhang 106 that has a length “K1” and a second overhang 108 that has a length “K2”. The first and the second overhangs 106, 108 of the first beam 100 extend from the vertical strut 104 in cantilevered fashion. Similarly, the second beam 102 of the I-beam 94 has a first overhang 110 that has the length “K1” and a second overhang 112 that has the length “K2”. The first and the second overhangs 110, 112 also extend from the vertical strut 104 in cantilevered fashion. In aspects of the disclosure, the length “K1” of the first overhangs 106, 110 of the first and second beams 100, 102 of the I-beam 94 is greater than the length “K2” of the second overhangs 108, 112 of the first and second beams 100, 102 of the I-beam 94. In aspects of the disclosure, the vertical strut 104 of the I-beam 94 supports, or is formed with, a cutting blade 114.

The vertical strut 104 of the I-beam 94 is received within the knife slots 42, 69, and 80 of the anvil plate 36, the channel member 64, and the cartridge body 72, respectively. The first beam 100 is received within the channel 38 (FIG. 8 ) of the anvil assembly 28, and the second beam 102 is received within the recess 68 a of the channel member 64 (FIG. 8 ). The vertical strut 104 of the I-beam 94 is positioned proximally of and in axial alignment with the guide member 86 of the actuation sled 78. When the drive assembly 90 is moved from its retracted position towards its advanced position, the I-beam 94 engages the channel member 64 and the anvil assembly 28 to move the tool assembly 16 from the open position (FIG. 1 ) to the clamped position (FIG. 7 ). In the clamped position, the staple forming surface 40 of the anvil assembly 28 and the tissue engaging surface 73 of the cartridge body 72 of the staple cartridge 62 define a tissue gap “G” (FIG. 8 ), and the cutting blade 114 (FIG. 6 ) of the I-beam 90 extends across the tissue gap “G”.

As the drive assembly 90 continues to move towards its advanced position, the I-beam 94 of the drive assembly 90 engages the actuation sled 78 (FIG. 5 ) and advances the actuation sled 78 from its retracted position towards its advanced position. As the actuation sled 78 moves towards its advanced position, the cam members 88 (FIG. 5 ) of the actuation sled 78 sequentially engage the pushers 76 to sequentially eject the staples 74 from the cartridge body 72 of the staple cartridge 62.

FIG. 9 illustrates tissue “T” after the tissue “T” has been stapled and cut along a cut line “CL” into two sections “T1” and “T2”. As illustrated, with the tool assembly 16 described above, four rows of staples 74 are applied to the tissue section “T1” and two rows of staples 74 are applied to the tissue section “T2”.

During a surgical procedure in which a section of diseased or damaged tissue “T2” of a patient is resected from healthy tissue “T1” of a patient, the tool assembly 16 can be used to provide a greater number of staples to the healthy tissue “T1” while providing an adequate number of staples to the diseased or damaged tissue “T2” to seal the tissue “T2” for removal. The added reinforcement to the healthy tissue “T1” minimizes the chance of septic leak from the healthy tissue “T1” which could cause complications to the patient and infection.

Persons skilled in the art will understand that the devices and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary aspects of the disclosure. It is envisioned that the elements and features illustrated or described in connection with one exemplary aspect of the disclosure may be combined with the elements and features of another without departing from the scope of the disclosure. As well, one skilled in the art will appreciate further features and advantages of the disclosure based on the above-described aspects of the disclosure. Accordingly, the disclosure is not to be limited by what has been particularly shown and described, except as indicated by the appended claims. 

What is claimed is:
 1. A tool assembly comprising: an anvil assembly including an anvil plate having a staple forming surface, the anvil plate defining a knife slot and staple forming pockets, the staple forming pockets positioned on opposite sides of the knife slot in the anvil plate; and a cartridge assembly coupled to the anvil assembly such that the tool assembly is movable between open and clamped positions, the cartridge assembly including a channel member and a staple cartridge, the channel member including side walls and a bottom wall that define a cavity, the bottom wall of the channel member defining a knife slot, the staple cartridge received within the cavity of the channel member and including a cartridge body, staples, pushers, and an actuation sled, the cartridge body defining a knife slot and staple receiving slots, the staple receiving slots positioned on opposite sides of the knife slot of the cartridge body, the knife slot in the channel member being axially aligned with the knife slot in the cartridge body, each of the staple receiving slots receiving one of the staples and one of the pushers, the actuation sled movable within the cartridge body into engagement with the pushers to sequentially eject the staples from the cartridge body; and a drive assembly including a drive member and an I-beam, the I-beam including a first beam, a second beam, and a vertical strut, the vertical strut extending through the knife slots of the anvil plate, the cartridge body, and the channel member, each of the first and second beams of the I-beam includes first and second overhangs that extend in cantilevered fashion from opposite sides of the vertical strut, the first overhang having a length that is greater than a length of the second overhang; wherein the tool assembly defines a central longitudinal axis, the knife slots of the anvil plate, the channel member, and the cartridge body of the staple cartridge being laterally offset from the central longitudinal axis of the tool assembly.
 2. The tool assembly of claim 1, wherein the knife slot in the anvil plate divides the staple forming surface of the anvil plate into a first surface that is positioned on a first side of the knife slot in the anvil plate and a second surface that is positioned on a second side of the knife slot in the anvil plate, and the staple forming pockets are aligned in rows in the first and second surfaces of the staple forming surface, the first surface of the staple forming surface having a greater number of rows of the staple forming pockets than the second surface of the staple forming surface.
 3. The tool assembly of claim 2, wherein the knife slot of the cartridge body divides the tissue engaging surface of the cartridge body into a first surface that is positioned on a first side of the knife slot in the cartridge body and a second surface that is positioned on a second side of the knife slot in the cartridge body, and the staple receiving slots are aligned in rows in the first and second surfaces of the tissue engaging surface, the first surface of the tissue engaging surface having a greater number of rows of the staple receiving slots than the second surface of the tissue engaging surface.
 4. The tool assembly of claim 3, wherein the first surface of the staple forming surface has four rows of the staple forming pockets and the second surface of the staple forming surface has two rows of the staple forming pockets, and the first surface of the tissue engaging surface has four rows of the staple receiving slots and the second surface of the tissue engaging surface has two rows of the staple receiving slots.
 5. The tool assembly of claim 4, wherein the actuation sled includes a body having a guide member and cam members, two of the cam members positioned on a first side of the guide member and one of the cam members positioned on a second side of the guide member.
 6. The tool assembly of claim 5, wherein the I-beam is movable through the anvil and cartridge assemblies to advance the actuation sled from its retracted position to its advanced position.
 7. The tool assembly of claim 1, wherein the vertical strut includes a cutting blade, and the tissue engaging surface of the cartridge body and the staple forming surface of the anvil plate define a tissue gap, the cutting blade positioned within the tissue gap when the tool assembly is in a clamped position. 